No specifics have really been set for that yet besides an old cranky witch, so any sort of mythic beast that you'd find in a forest or plains is likely to be found. The Forest at night is sort of a haven for all sorts of beasties, comparable to a party house when the parents out of town. When the wall of thorns creeps up to keep the humans out, any number of creature can be found roaming around and none of them will be happy to see anything that resembles a hero type breaking up their party.

Hope that helps!